Del-1 (developmentally regulated endothelial cell locus-1) protein (sometimes just referred to as “Del-1” or the “full-length Del-1”) is a protein which has EGF (epithelial growth factor)-like domains and discoidin-I-like domains. This protein is an extracellular matrix protein and is known to bind to a protein called αvβ3 integrin receptor or αvβ5 integrin receptor on the surfaces of vascular endothelial cells via the EGF-like domain to thereby promote adhesion of the endothelial cells onto extracellular matrix (Hidai, C. et al., GENES & DEVELOPMENT 12:21-33, 1998).
Recently, a gene encoding the full-length Del-1 has been cloned. It is presumed that the full-length Del-1 is capable of binding, via a part or the entire region thereof, to proteoglycan present in extracellular matrix. A method based on this binding is known in which the full-length Del-1 is expressed; a specific molecule (e.g., a protein or proteoglycan) is bound to the resultant full-length Del-1; and then the molecule bound to the full-length Del-1 (e.g., a protein or proteoglycan) is recovered (see, for example, Japanese Unexamined Patent Publication/PCT No. H11-507527).
Therefore, identification of these binding sites and analysis of the mode of binding are important for recovering molecules of interest and investigating into molecules which bind to the full-length Del-1.
However, since the ability of the full-length Del-1 to deposit onto extracellular matrix is not so high, molecules of interest bound to the full-length Del-1 could not have been recovered sufficiently.